Many different types of abrasive articles exist in the art. These include coated abrasives, non-woven abrasives and bonded abrasives. Each type of abrasive article is designed for a specific use. For example, a specific type of a coated abrasive is a lapping film. Lapping films may be used in abrasive processes requiring a fine finish without excessive heat generation. One example is the polishing of fiber optic connectors.
Fiber optic connectors of a wide variety of designs have been employed to terminate optical fiber cables and to facilitate the connection of the cables to other cables or other optical fiber transmission devices. A typical optic fiber connector includes a ferrule, which mounts and precisely positions an optical fiber or fibers within the connector. The ferrule may be fabricated of ceramic materials.
A typical single mode fiber optical connector may include a glass core with an outer diameter of about 9 microns surrounded by a glass cladding with an outer diameter of about 125 microns (collectively the “glass fiber”). A ferrule then surrounds the glass fiber. The ferrule has an outer diameter of about 2.0 millimeters at its outer ends and the diameter increases along a beveled edge (approximately 45°) to about 2.5 millimeters at its widest portion. During manufacture, the glass fiber is threaded through the ceramic ferrule and attached with an epoxy resin. The excess glass is then cleaved from the newly formed fiber optical connector, and the ends are polished to a fine finish.
A pair of fiber optic connectors or a connector and another optical fiber transmission device often are mated in an adapter that aligns the fibers to provide good transmission. The adapter couples the connectors together so that their encapsulated fibers connect end-to-end to permit the transmission of light. The adapter may be an in-line component, or the adapter may be designed for mounting in an opening in a panel, backplane, circuit board or the like.
The polishing of the connectors is a necessary and important step. Light travels through the glass fiber across the junction to the next connector. In order to achieve a good transmission of the light, the ends must be highly polished, and the polished ends of the glass fiber and the ceramic ferrule may lie within a common planar or slightly convex surface. A planar or slightly convex surface with a radius of curvature of between about 10 millimeters and about 20 millimeters gives maximum glass fiber core contact area with the glass fiber core in the adjacent connector. With good transmission of light across the junction, the backreflection of the connection, a measure of the amount of light lost across the junction, will be minimized.
Single mode fiber optic connectors are currently finished with a series of abrasive lapping films, most commonly starting with a coarse grade of silicon carbide, then several progressively finer grades of diamond, and finally a very fine grade of silica. The finishing of the connectors requires very precise cutting properties at each step so that the geometry of the fiber optic remains optimal, and at the same time requires that the polished connector have no defect flaws such as scratches, pits, or deposits. One common deposit on connectors is known in the industry as “resin transfer”. The source of the resin in not well known, it may be from the lapping films, from the epoxy used in creating the connector, or a combination of both. It presents itself, however, as a smear that can be readily seen at 200× under an optical microscope.
Resin transfer may be affected by the binder chosen and the combination of the binders. Additionally, the level of cure of a binder has an effect on resin transfer. Resin transfer can also be affected at the end user level, for instance by the use of isopropanol/water or soap/water blends as a working liquid. This is a generally undesirable means of control, however, for a lapping film vendor because many end users have a strong preference to simply use water since a water-only system is more environmentally friendly. Resin transfer can also be affected by the polishing conditions employed, but usually cannot be controlled by these parameters. In any case, this is also undesirable for lapping film vendors, because each fiber optic polishing operation is slightly different, requiring different optimal processes, which the end user may be unwilling or unable to follow.
The invention involves the addition of additives to abrasive article such that the use of the modified abrasive article exhibits substantially less resin transfer.